Cementing material



I Patented May 11 1937 UNITED STATES CEMENTING MATERIAL James F. Walsh,South Orange, Harry E. Smith and Amerigo F. Caprio, Newark, N. 1.,asslgnors to Celluloid Corporation, a corporation of New Jersey NoDrawing. Application Ma 12, 1930, Serial No. 451,862

13 Claims.

This invention relates to the preparation of a cementing material forthe compositing or lamination of sheets of cellulosic plastics.

An object of our invention is to prepare a sheet or film of plasticmaterial adapted to be em ployed as an adhesive or cementing materialfor causing layers of plastic compositions containing derivatives ofcellulose to adhere to each other or to the surfaces of other material.'Further objects of our invention will appear from the followingdetailed description.

In cementing or compositing celluloid sheets. the practice has been touse volatile solvents such as acetone, alcohol, butyl acetate, etc. Saidcements however are not always satisfactory, especially when coloredcellulosic plastic sheets are cemented. In this case when the cement isbrushed on the sheet, the colors have a tendency to run thus spoilingthe configuration and color effects desired. This trouble is alsoexperienced with celluloid sheets that have been printed and which arecemented in this manner, since the ink is dissolved by the activesolvents and the letters become smeared and lose their sharp outline.

5 Spraying such sheets with liquid solvent is also objectionable, sincethe powerful action of the I solvents tends eventually to warp ordistort the sheets. This isa rather serious defect, since the cellulosicplastic stock becomes green and 30 shrinkage and buckling difllcultiesdevelop upon use.

The need of a cementing medium to overcome all these difficulties hasbeen great. We have found that thin flexible sheets of a plastic com- 35position containing a derivative of cellulosev and a relatively largeamount of a plasticizer comprising an alkyl ester of phthalic acid maybe used as an intermediate layer between two sheets to be cemented. Uponthe application of heat 40 and pressure, a fusion or-bond between thesheet is effected without the further application of a liquid cement. Bythe use of such sheets as the cementing material, all the objectionsarising, from the use of a volatile solvent are 45 avoided.

In accordance with our invention, we prepare sheets or films containinga derivative of cellulose and a relatively-large proportion of a plas--ticizer comprising an allwl phthalate, which 50 sheets are adapted to beused as an, adhesive or cementing agent for causing films, sheetsor'other articles made of cellulosic plastics to adhere to each other orto the surfaces of other materials. The cementing or adhesive sheet maycontain 55 any suitable derivative of cellulose such as cellulosenitrate or pyroxylin .or organic derivatives of cellulose and celluloseethers. Examples of such organic derivatives of cellulose are celluloseacetate, cellulose formats, cellulose propionate 60 and cellulosebutyrate, while examples oi cellulose ethers are ethyl cellulose, methylcellulose and benzyl cellulose.

As stated, we employ an alkyl ester of phthalic acid in the plasticizer.Examples of such alkyl phthalates are dimethyl phthalate, diethylphthalate, methyl ethyl phthalate, dibutyl phthalate or diamylphthalate. One or more of these alkyl phthalates may be used as the soleplasticizer.

In many cases, however, other plasticizers may also be added to thecomposition of the cementing sheet. Examples of these plasticizers arecamphor, diethyl tartrate, dibutyl tartrate, triphenyl phosphate,para-ethyl-toluene-sulfonamid, etc. The choice of such plastioizer willdepend upon the derivative of cellulose present. The total amount ofplasticizer employed will generally vary from 50 to 150% or more of theweight of the derivative of cellulose present. The amount of plasticizerwill be governed by the degree of heat and pressure to be employed inthe cementing operation, generally the higher the temperature andpressure employed in such operation, the smaller will be the amount ofplasticizer employed.

Often it is desirable to add higher boiling volatile solvents such asbutyl acetate, diacetone alcohol, ethyl lactate, the ethyl ether ofethylene glycol, etc.,to the composition from which the adhesive sheetsare made, since their presence tends to keep the sheets soft and easilycementable.

If the sheets are to be employedfor causing the cellulose plastics toadhere to surfaces of metal or other smooth surfaces, it is advisable toincorporate a resin compatible with the derivativeof cellulose in thesame. In. the case of cellulose nitrate or pyroxylin, ester gum may beemployed, while in the case of cellulose acetate accaroid resin, thefusible and soluble phenolformaldehyde condensation resins ortoluenesulfonamid-formaldehyde resins may be used. The amount of resinadded may be from 30 to 100% of the weight of the derivative ofcellulose present in the cement sheets.

Pigments, dyes, fillers or other effect materials may be added, as maybe also stabilizers such-as urea, etc.

vIn making the adhesive or cementing sheets, the cellulose derivativesand plasticizers may be mixed together with other ingredients that areto be present with suitable volatile solvents or latent solvents such asacetone, ethyl alcohol, methyl alcohol, benzol or suitable mixtures ofthese. The choice of solvents or solvent mixtures depends upon thesolubility characteristics of the particular cellulose derivativeemployed. The mass may be converted or gelatinized by kneading atelevated temperatures and then treated with heated malaxating rolls,and. then further worked up into sheet form by any known method.Solutions of the cellulose derivative and plasticizers may be cast onpolished surfaces to form films upon evaporation of the volatilesolvent. The sheets are formed to have thicknesses of from 0.003 to0.020" or more. We have found thicknesses of 0.005 to 0.010 and 0.020"produce very satisfactory results. The sheets are preferably usedunpolished.

In employing the adhesive or cementing sheets made in accordance withthis invention, the same are inserted between the films, sheets orlayers of cellulosic plastic that are to be united, and the assembly isthen pressed at elevated temperatures. Likewise such adhesive sheets maybe inserted between a layer of cellulosic plastic and the surface ofmetal or wood and lamination caused by the application of heat andpressure. The amount of heat and pressure employed will depend on thepercentage of plasticizers present and also the presence of high boilingsolvents, the greater percentage of these present, the less heat orpressure required.

Thus an adhesive sheet containing equal parts of pyroxylin andplasticizercan be readily cemented at a temperature corresponding toonly 10lbs.per square inch steam pressure and under a hydraulic pressure500 lbs. per square inch for 10 minutes. Where only slight pressure andheat are available, the adhesive sheets may be subjected to the vaporsof solvents prior to lamination.

In order further to illustrate our invention but without being limitedthereto, the following specific examples are given.

' Example I The following is a formula for making adhesive sheetscontaining pyroxylin.

Parts by weight If desired the carnphor may be omitted entirely, inwhich case 75 parts of diethyl phthalate is employed. Other desirableresults are obtained when diethyl phthalate is replaced by dibutylphthalate.

Example [I p The following are examples or formulae for making adhesivesheets containing cellulose acetate.

- Parts by weight (a) Cellulose acetate 100 Triphenyl phosphate 10Para-ethyl-toluene sulfonamid 25 ,Dimethyl phthalate 25 Triacetin; 20Volatile solvent q s Partsby weight (b) Cellulose acetate 100 Dimethylphthalate 45 Para-ethyl-toluene sulfonamid 25 Triacetin l5 Volatilesolvent (Ls.

The adhesive sheets made in accordance with this invention are flexibleand are readily applied between the two sheets to be cemented. There isno running of color, no color absorption, and the cementation can belimited to any particular section desired. The il 9f cementable sheetsmade in accordance with this invention is quite advantageous for manypurposes.

They are dry, non-sticky,'easily applied and the union or amalgamationis perfect.

The foregoing examples are given merely by way of illustration, and manyvariations may be made therein without departing from the spirit of ourinvention.

Having described our invention, what we de sire to secure by LettersPatent is:

1. Method of causing the surface of a layer of plastic compositioncontaining a derivative of cellulose to adhere to another surfacewithout the aid of low-boiling solvents comprising interposing betweenthe surfaces a preformed sheet containing a derivative of cellulose,relatively high boiling solvents and a plasticizer comprising an alkylphthalate present in proportion of from 50 to 100% on the weight of thederivative of cellulose and applying heat and pressure.

2. .Method of causing vthe surface of a layer of plastic compositioncontaining a derivative of cellulose to adhere to another surfacewithout the aid of low-boiling solventscomprising interposing betweenthe surfaces a preformed sheet containing a derivative of cellulose, aresin and a plasticizer comprising an alkyl phthalate present inproportion of from 50 to 100% on the weight of the derivative ofcellulose and applying heat and pressure.

3. Method of causing the surface of a layer of plastic compositioncontaining a derivative of cellulose to adhere to another surfacewithout the aid of low-boiling solvents, which comprises interposingbetween the surfaces a preformed sheet containing cellulose nitrate,relatively high boiling solvents and a plasticizer comprising an alkylphthalate present in proportion of from 50 to 100% on the weight of thecellulose nitrate and applying heat and pressure.

4. Method of causing the surface of a layer of plastic compositioncontaining a derivative of cellulose to adhere to another surfacewithout the aid of low-boiling solvents, which comprises Anterposingbetween the surfaces a preformed sheet containing cellulose nitrate, aresin and a plasticizer comprising an alkyl phthalate present inproportion of from 50 to 100% on the weight of the cellulose nitrate andapplying heat and pressure.

5. Method of causing the surface of a'layer of plastic compositioncontaining a derivative of' cellulose to adhere to another surfacewithout the aid oflow-boiling solvents, which comprises interposing.between the surfaces a preformed sheet containing cellulose acetate,.relatively high'bolling solvents and a plasticlzer comprising an alkyl i-hthalate present in proportion of from 50 to 100% on the weight of thecellulose acetate and applying heat and pressure.

6. Method of causing the surface of a layer of plastic compositioncontaining a derivative of cellulose to adhere to another surfacewithout the aid of low-boiling solvents, which comprises interposingbetween the surfaces a preformed sheet containing cellulose acetatefaresin and a plasticizer comprising an alkyl phthalate present inproportion of from 50 to 100% on the. weight of the cellulose acetateand applying heat and pressure.

'7. Method of causing the surface of a layer of plastic compositioncontaining a derivative of cellulose to adhere to another surfacewithout the aid of low-boiling solvents, which comprises interposingbetween the surfaces a preformed sheet containing a derivative ofcellulose, relatively high boiling solvents and a plasticizer selectedfrom the group consisting of dimethyl phthalate and diethyl phthalate,said plasticizer being present in a proportion of from 50 to 100% on theweight of the derivative of cellulose, and applying heat and pressure. H

8. A sheet adapted to be employed as a cementing agent for cellulosicplastics, which sheet contains aderivative of cellulose, relatively highboiling solvents and a plasticizer comprising an alkyl phthalate, theamount of plasticizer present being in a proportion of from 50 to 100%on the weight of the derivative of cellulose.

9. A sheet adapted to be employed as a cementingagentior cellulosicplastics, whichsheet contains a derivative of cellulose relatively highboiling solvents and a plasticizer comprising an' 2oalky1 phthalate, theamount of plasticizer present being in a proportion of from 50 to 100%on the weight of the derivative of cellulose.

10. .A sheet adapted to be employed as a cementing agent for cellulosicplastics, which sheet contains a derivative of cellulose, a resin and aplasticizer comprising an alkyl phthalate, the amount of plasticizerpresent being in a proportion of from to on the weight of the derivativeof cellulose.

11; A sheet adapted to be employed as a. cementing agent for cellulosicplastics, which sheet contains cellulose nitrate, relatively highboiling solvents and a plasticizer comprising an alkyl phthalate; theamount of plasticizer present being in a proportionoi from 50 to 100% onthe weight of the cellulose nitrate.

boiling solvents and a plasticizer selected from the group consisting ofdimethyl phthalate and diethyl phthalate, the amount 01' plasticizerpresent being in a proportion of from 50 to 100% on the weight of thederivative of cellulose.

' JAMES F. .WALSH. HARRY E. SMITH. AMERIGO 1". CAPRIO.

